The use of ophthalmic lenses for the correction of ametropia is well known. For example, multifocal lenses, such as progressive addition lenses (“PALs”), are used for the treatment of presbyopia. The progressive surface of a PAL provides far, intermediate, and near vision in a gradual, continuous progression of increasing dioptric power from far to near focus.
Any number of methods for designing spectacle lenses are known. Typically, these methods involve one or more of benchmarking of known designs, developing theoretical target values for control optical parameters, obtaining subjective patient feedback, and using objective testing methods to produce a lens design. One disadvantage of these design methods is that they do not correlate the patient feedback and objective testing to precise locations on the lens. Thus, the point at which an individual's line-of-sight actually intersects with the lens' surface while the individual is performing a given task frequently differs from that calculated by the lens designer. This results in the lens wearer, especially the PAL wearer having to move the eye and head to maintain adequate visual resolution through the lens.
Additionally, it is known that certain parameters control optimal visual comfort for the lens wearer. These parameters include, without limitation, clarity of vision, comfort over sustained periods of use, ease of changing focus, and the amount of head and eye movement required by the lens wearer. Conventional design methods do not account for these parameters with any precision and provide little to no guidance for design optimization processes requiring definition of merit functions incorporating one or more of these parameters. Therefore, a method for designing lenses that overcomes these disadvantages is needed.